package com.cory.utils.security;

import java.security.GeneralSecurityException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import com.cory.utils.lang.ExceptionUtils;
 
/**
 * DH安全编码组件
 */
public abstract class DHCoder {
    public static final String ALGORITHM = "DH";
 
    /**
     * 默认密钥字节数
     * 
     * <pre>
     * Default Keysize 1024  
     * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
     * </pre>
     */
    private static final int KEY_SIZE = 1024;
 
    /**
     * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。
     */
    public static final String SECRET_ALGORITHM = "DES";
    
    private static final String PUBLIC_KEY = "DHPublicKey";
    private static final String PRIVATE_KEY = "DHPrivateKey";
 
    /**
     * 初始化密钥
     * 
     * @return
     */
    public static Map<String, Object> initKey() {
    	try{
	        KeyPairGenerator keyPairGenerator = KeyPairGenerator
	                .getInstance(ALGORITHM);
	        keyPairGenerator.initialize(KEY_SIZE);
	 
	        KeyPair keyPair = keyPairGenerator.generateKeyPair();
	 
            // 甲方公钥
	        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
	 
            // 甲方私钥
	        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
	 
	        Map<String, Object> keyMap = new HashMap<String, Object>(2);
	 
	        keyMap.put(PUBLIC_KEY, publicKey);
	        keyMap.put(PRIVATE_KEY, privateKey);
	        return keyMap;
    	} catch (GeneralSecurityException e) {
			throw ExceptionUtils.unchecked(e);
		}
    }
 
    /**
     * 根据对方公钥初始化密钥
     * 
     * @param publicKey 甲方公钥
     * @return
     */
    public static Map<String, Object> initKey(byte[] key) {
    	try{
	        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
	        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
	        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
	 
            // 由甲方公钥构建乙方密钥
	        DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();
	 
	        KeyPairGenerator keyPairGenerator = KeyPairGenerator
	                .getInstance(keyFactory.getAlgorithm());
	        keyPairGenerator.initialize(dhParamSpec);
	 
	        KeyPair keyPair = keyPairGenerator.generateKeyPair();
	 
            // 乙方公钥
	        DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
	 
            // 乙方私钥
	        DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
	 
	        Map<String, Object> keyMap = new HashMap<String, Object>(2);
	 
	        keyMap.put(PUBLIC_KEY, publicKey);
	        keyMap.put(PRIVATE_KEY, privateKey);
	 
	        return keyMap;
    	} catch (GeneralSecurityException e) {
			throw ExceptionUtils.unchecked(e);
		}
    }
 
    /**
     * 加密<br>
     * 
     * @param data 待加密数据
     * @param publicKey 对方公钥
     * @param privateKey 己方私钥
     * @return
     */
    public static byte[] encrypt(byte[] data, byte[] publicKey, byte[] privateKey) {
    	try{
            // 生成本地密钥
	        SecretKey secretKey = getSecretKey(publicKey, privateKey);
	 
            // 数据加密
	        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
	        cipher.init(Cipher.ENCRYPT_MODE, secretKey);
	 
	        return cipher.doFinal(data);
    	} catch (GeneralSecurityException e) {
			throw ExceptionUtils.unchecked(e);
		}
    }
 
    /**
     * 解密<br>
     * 
     * @param data 待解密数据
     * @param publicKey 对方公钥
     * @param privateKey 己方私钥
     * @return
     */
    public static byte[] decrypt(byte[] data, byte[] publicKey, byte[] privateKey) {
    	try{
            // 生成本地密钥
	        SecretKey secretKey = getSecretKey(publicKey, privateKey);
            // 数据解密
	        Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
	        cipher.init(Cipher.DECRYPT_MODE, secretKey);
	 
	        return cipher.doFinal(data);
    	} catch (GeneralSecurityException e) {
			throw ExceptionUtils.unchecked(e);
		}
    }
 
    /**
     * 构建密钥
     * 
     * @param publicKey 公钥
     * @param privateKey 私钥
     * @return
     * @throws GeneralSecurityException
     */
    private static SecretKey getSecretKey(byte[] publicKey, byte[] privateKey) 
    		throws GeneralSecurityException {
 
        KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKey);
        PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
 
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKey);
        Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);
 
        KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
                .getAlgorithm());
        keyAgree.init(priKey);
        keyAgree.doPhase(pubKey, true);
 
        // 生成本地密钥
        SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);
 
        return secretKey;
    }
 
    /**
     * 取得私钥
     * 
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static byte[] getPrivateKey(Map<String, Object> keyMap) {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
 
        return key.getEncoded();
    }
 
    /**
     * 取得公钥
     * 
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static byte[] getPublicKey(Map<String, Object> keyMap) {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
 
        return key.getEncoded();
    }
    
}
